add/remove capabilities to user roles

Change Roles

$edit_editor = get_role('editor');
$edit_editor->add_cap('add_users');
$edit_editor->add_cap('create_users');
$edit_editor->add_cap('delete_users');
$edit_editor->add_cap('edit_users');
$edit_editor->add_cap('list_users');
$edit_editor->add_cap('edit_theme_options');